Aged Reflectance, Emittance and the Alteration Trigger
Under the 2025 California Energy Code, a flat commercial roof has to show an aged solar reflectance of at least 0.63 together with a thermal emittance of 0.75, or else an SRI of 75. Reflectance is how much sunlight the surface sends back, and emittance is how readily it lets go of the heat it does absorb, so a bright surface with poor emittance falls short. The rule reaches every new roof and any alteration touching more than half the roof area, or 2,000 square feet when that is the lesser figure, and the city's permit center has treated the 2025 codes as enforced since January 1, 2026.
That threshold matters on a repair that grows. A patch over one bay stays small, but a project that quietly spreads across half the roof can pull the whole roof into the requirement. We read the maker's rated aged values before ordering, match them to the required figures, and confirm with the city when a project sits near the line. Installing it so it still holds those values years later is where the work is.
Matching the Surface to the Roof Beneath
Which reflective system goes on depends on what is underneath. A white TPO sheet or a PVC sheet suits a replacement or recover, with welded seams and prefabricated corners where the manufacturer provides them. A sound modified bitumen, built-up or metal roof can often take a silicone or acrylic coating once it has been cleaned, repaired and primed. Where the old roof holds wet insulation, a coating only hides the trouble, and we say so before anyone spends money on it.
The metal gets the same attention as the membrane. Coping, counterflashing and curb caps are formed from material that matches the reflective surface, soldered or sealed at the laps, and finished with a tooled sealant joint, so a dark strip of old edge metal does not sit along a bright roof. Seams are tested, fasteners are covered, and the termination at each wall is checked against the reglet before the surface goes down.
Heat Load and Class A in the Foothills
Pasadena holds a recorded high of 113 F in June, and the dry summer leaves roofs in direct sun for months with almost no rain to rinse them. A reflective surface keeps the roof cooler, which lowers the thermal cycling on seams and flashings and lightens the load on the cooling equipment sitting on it. In the historic brick-facade blocks of Old Pasadena, where small offices occupy the upper floors, that difference reaches the top-floor tenants first.
Reflective does not mean fire rated. Pasadena's mapped fire zones lie generally in the Arroyo Seco and upper Hastings Ranch, and a property in the Very High tier needs a Class A rating from the whole assembly of covering, underlayment and deck, required wherever more than half an existing roof is replaced in a year. A white membrane that meets the cool roof numbers still has to be listed in a Class A assembly to be used there. We check both ratings together before a system is chosen, because the second one is easy to forget until the permit is reviewed.
Washing, Inspecting and Recoating
A cool roof holds its numbers when someone looks after it. Light washing once the dry season has coated it with dust restores much of the surface, seams and flashings get a visual check at the same visit, and a coating is recoated before the film wears thin enough to expose the substrate. Foot traffic around equipment scuffs the surface, so walkway pads along service routes keep the bright sheet from turning into a gray path. A maintenance program puts those checks on a schedule in place of leaving them to chance.
When an older roof reaches the end of its life, the reflective system is part of the answer, not an afterthought. A sound roof can often gain years from roof coating restoration, while a failed roof is better served by replacement with a new reflective sheet.
Commercial Roofing Questions
Does every new commercial roof in Pasadena have to be a cool roof?
Nearly every low-slope nonresidential roof that is new, or altered across more than half its area or 2,000 square feet, must meet the aged reflectance and emittance values in the California Energy Code. We confirm which side of that line your building sits on at the start of the scope.
How much cooler will the top floor feel after the work?
Mostly on the floor directly under the roof, and the amount changes with insulation, ceiling height and the equipment working below, so a degree figure belongs to the building and not to the product. The roof surface itself runs cooler in July than a dark membrane does.
Can my existing dark roof be coated to meet the requirement?
Often, if the membrane is sound and the insulation beneath it is dry. A moisture survey tells us which, and cleaning, repair and primer come before any reflective film. A roof with trapped water or a badly worn surface is better replaced, since the coating would only hide those conditions for a season or two.
Does a reflective roof conflict with a Class A requirement in the foothills?
The two ratings are independent, so the finished assembly has to carry both. Reflectance is a surface property, and Class A is judged on covering, underlayment and deck together. Many reflective systems are listed in Class A assemblies, and we select one from that group when the building sits in a mapped zone.
Will a white roof show dirt and need washing?
It will, and that is the reason aged values exist. A roof that is washed lightly each dry season and checked at the seams keeps close to its rated reflectance. One that is never touched slides off the number slowly, and the first sign is a gray band along the base of the walls.
